Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$222.94	7.717%	$240.1443	$240.14	$240.15	$240.10
Purchase #2	$37.96	7.810%	$40.9247	$40.92	$40.90	$40.90
Purchase #3	$59.58	11.762%	$66.5878	$66.59	$66.60	$66.60
Purchase #4	$17.81	12.470%	$20.0309	$20.03	$20.05	$20.00
Purchase #5	$150.55	5.579%	$158.9492	$158.95	$158.95	$158.90
Purchase #6	$163.86	4.746%	$171.6368	$171.64	$171.65	$171.60
Purchase #7	$233.55	6.575%	$248.9059	$248.91	$248.90	$248.90
7 purchase totals =	$886.25		$947.1796	$947.18	$947.20	$947.00